The sensor of the D7100 is better than the one in the D7000, in general. If one prints both, starting at ISO 100 and goes up in ISO settings, the typical D7100's image will be a bit better in most aspects than the typical D7000's image, including the "grain" that some here are complaining about and which does not make much sense. The D800, at 36 MP, at full res, has "more grain" than the D700, at 12MP.

At ISO 100, the D800 is pure silk compared to the D700, which is noticeably noisier than the D7000 in sky and shadow at low ISO. (One reason I never bought one.) At about ISO 800, the D700 pulls ahead of the DX cameras.

But if one resizes the D800's image to 12MP, it'll be cleaner the D700's. And if one needs to print larger, the D800's and the D7100's files will be better as well.

Secondly, the D7100's image retain better color as ISO goes up, compared to the D7000's, this shows even at full res.

Thirdly, the D7100's AF is certainly better thna the D7000, but of course one needs to learn how to use it to its full capabilities.

There are other aspects where the D7100's body is better than the D7000's, in some inetresting ways.

Finally, one cannot expect the sensor technology to make big jumps with every release. The technology is reaching a (very high ) plateau. These cameras are amazing in so many aspects, people don't realize how far digital technology has come in only a decade or so of commercially available cameras. AF is the same story. This is likely more evident for those that used film for a long period, since back then, 10 years usually meant very little in technology advancement, be it either in film or camera tech.

I've seen more than enough to get the message that the D7100 is closer to the D800e than the D7000 in resolution, color wonderfulness and microcontrast. Which is a big jump in my book. Not buying one, just reporting my findings.